The present invention relates to a photosensitive mixture that contains a polymeric compound with lateral olefinically unsaturated radicals and a photosensitive compound. The photosensitive mixture of the present invention is outstandingly suitable for producing printed circuits via resist technique and in particular, for producing lithographic printing plates used in offset printing.
Photosensitive mixtures are described in German Offenlegungsschrift No. 2,053,364 that contain reaction products of polymers containing hydroxyl or amino groups and unsaturated sulfonyl isocyanates and also an initiator and optionally further polymerizable compounds. Reaction products of the same type are described, in combination with diazonium salt polycondensates or low molecular azides, in German Offenlegungsschrift No. 3,036,077.
A disadvantage of these mixtures is, on the one hand, the complicated and expensive production of the necessary alkenylsulfonyl isocyanates. Moreover, the printing plates produced therefrom exhibit an inadequate ink receptivity, so that an unacceptably high output of waste paper is produced in the proofing process and after a prolonged stoppage. In particular, mixtures according to German Offenlegungsschrift No. 2,053,364, which contain exclusively a photoinitiator and the light-curable polymer described, have only a very low photosensitivity and a poor resistance to abrasion. Consequently, long-run lithographic printing plates cannot be produced with these materials.
From German Offenlegungsschrift No. 2,053,363 mixtures are known that contain, as binders, reaction products of polymers containing hydroxyl or amino groups and at least one saturated alkyl-, alkoxy-, aryl- or aryloxysulfonyl isocyanate. The binder is in this case processed in combination with diazonium salt condensation products or photopolymerizable mixtures to form photosensitive layers. The mixtures obtained in this process can, however, be developed under aqueous and alkaline conditions only if the binders used have high acid numbers, as a result of which the abrasion resistance and the printing properties of the cured layer are adversely influenced.